The properties of the products obtained in the cellulose decomposition process conducted in near-critical water were analyzed using HPLC, CPC and IR. The properties of the products changed with the progress of the reaction and a reaction model consisting of the formation process of water solubles (WS) and the subsequent second decomposition process was proposed. The WS formation process is a saccharification process where hydrolysis preferentially progresses. The second decomposition process is a carbonization process of WS, where the elimination of functional groups leads to the formation of gaseous products and insolubilization of WS. The hydrolyzate solution obtained in the saccharification process could be used as a feedstock of ethanol fermentation and the fermentation rate of the solution was improved by removing furfurals with an active carbon treatment. Copyright (C) 1997 Elsevier Science Ltd.